PEAVEY CEL 2 User Manual
O WNER’ S M ANUAL
CEL 2
2 Channel Compressor Expander Limiter
™
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2
CEL™2 DUAL COMPRESSOR/EXPANDER/LIMITER
GENERAL DESCRIPTION:
Thank you for purchasing the CEL™2 dual compressor/expander limiter. The following manual
contains a detailed description, function and specification of your CEL™2.
The CEL
™
2 compressor is a single rack space dual compressor. It can be operated either as two
independent compressors, or as a synced stereo compressor with true RMS summing. High quality
voltage controlled amplifier (VCA) and RMS-rectifier integrated circuits are used to maintain low
distortion and excellent noise performance.
A soft knee topology is used for each function to provide smooth transition curves. (When the
circuits become active, the gain change is phased in rather than instantaneously applied.) This
causes compression and limiting to be less obvious and more pleasing to the ear, as well as being
easier to adjust for the desired result.
The downward expander section has threshold and ratio adjustments to allow it to be used for
noise reduction (slight ratio) or a gate (high ratio). The compressor has attack and release controls
in addition to threshold and ratio controls for complete versatility. Any level lost due to compression
can be made up by the output level control.
The limiter is an infinite ratio compressor that keeps the output from exceeding a level set
by its threshold control and has only one adjustment. It is totally independent of the compressor
’
s
settings and can be used to stop peaks from getting through when only mild compression (low ratio)
is desired. It has its own LED (with a half-second peak hold time) to indicate when it has been
activated.
Each section (expander, compressor or limiter) can be set so that it is disabled either by a
threshold or ratio adjustment.
A side-chain insert in the detector path allows manipulation of the detector signal. The control
signal can be frequency shaped or replaced for de-essing, or ducking purposes. It is engaged by a
front panel switch. If this switch is pressed with nothing connected to the rear panel side-chain TRS
jack, the signal from the opposite channel is fed to the detector, and the compressor ducks when
there is signal on the other channel without the need for cross patching (the compressor controls will
set how it functions). If an external equalizer is inserted into the path, normal side-chain functions
(de-essing, rumble filtering, etc.) can be accomplished.
A dual-mono/stereo link switch sums the RMS detected levels of each channel together to
accurately represent the stereo signal’s amplitude. This amplitude voltage is used to control both
VCAs. In this mode, only the controls associated with channel Afunction. The gain reduction LED
array of channel B is turned off to give a visual clue as to which knobs are operational.
There are two twelve segment LED arrays that show the output level and the amount of gain
reduction. By watching the gain reduction meter, the action of an adjustment is readily apparent and
easy to set. The output level can be set to achieve the best signal to noise ratio.
A hard-wired bypass switch disengages all functions and operates even when the unit is not
powered.
3
ENGLISH
CONTROL FUNCTIONS:
(1) EXPANDER THRESHOLD: Sets the level at which the downward expander begins operation.
(If it is set at the minimum position, the threshold is so low that the expander never activates, effectively disabling it.) If the input signal drops below the threshold’s set point, the expander fades it out
according to the slope (ratio) set by the expander RATIO control. The soft knee design smoothes the
transition from off to active by dynamically shifting the slope through the transition point. The attack
and release times are preset for fast action.
(2) EXPANDER RATIO: The expander ratio is determined by dividing the input level by the output
level. Aratio of 1:3 signifies that the output level has dropped three times as fast as the input. Aratio
of 1:1.1 has such a slight slope that it is barely audible. Ratios of 1:1.2 to 1:2 are typically used to
eliminate background noise and to dampen room reverberations. Higher ratios are used when gating
is required.
(3) COMPRESSOR THRESHOLD: Sets the point that compression action begins. Any signal
above this threshold will be compressed at the amount set by the compressor ratio control. If it
drops below this point, the compressor has no effect. At the maximum setting, the compressor will
be out of circuit for all signals except very high peaks. At the minimum setting, the source will be
almost continuously compressed.
(4) COMPRESSOR RATIO: Varies the amount of compression. It is the ratio of the input level to
the output level. Aratio of 4:1 signifies that the input level has increased four times as fast as the
output (the dynamic range is compressed by a factor of four). If the ratio is 1:1 the output exactly
tracks the input, and there is no compression. Ratios of 2:1 to 4:1 are typically used for vocals and
musical instruments. Higher ratios provide a soft limiting function, since the compressor uses the
same soft knee design as is used in the expander (see #1).
(5) COMPRESSOR ATTACK: Sets the speed at which the compressor circuit responds to an
increase in the input level. Minimum settings allow it to act quickly so that fast transients do not get
through. High settings slow down the response time to let the signal settle before acting upon it.
(Useful for those situations when you want percussive attacks, but still need compression.)
(6) COMPRESSOR RELEASE: Sets the time which the compressor circuit takes to track the input
after a drop in level. Low settings will cause the compressor to follow the signal closely, so that rapid
input changes will not be lost during compression. Higher settings will cause the compressor to
disengage more gradually, which helps reduce pumping and breathing.
(7) LIMITER THRESHOLD: The limiter is an infinite ratio compressor. The threshold control
defines the point that absolute limiting begins. The limit LED will light and hold for half a second (to
make transients visible) when this threshold has been exceeded. To disable limiting, set this control
to maximum.
4
FRONT PANEL
3 4 5 6 7 13 1 2 3 4 5 6 7 1488
9
2
10 109
11 12
12
1511
1
(8) OUTPUT LEVEL: Adjusts the post-processing gain to make up for compression loss. It
does not adjust the input level. The input levels should be set by the source equipment to 0 dBu
(1/4" jacks) or +4 dBu (XLR jacks) for best noise performance. The output level is monitored by an
LED meter to give a visual indication of signal strength.
(9) GAIN REDUCTION METER: Atwelve segment LED array that tells how much gain reduction
is being applied to the signal. If this meter is not active, there is no change to the input signal. It is
very useful for making adjustments, since the action of all controls is easily seen.
(10) OUTPUT LEVEL METER: This is a peak indicating meter that is connected to the output jack.
The 0 dB point is 0 dBu for the 1/4" jacks and +4 dBu for the XLR jacks.
(11) EXTERNAL SIDE CHAIN ENABLE: The side chain is actually an alternate loop inserted into
the detector path. This switch enables external processing. Frequency shaping can be applied for
de-essing (add a 2 kHz to 6 kHz bandpass filter) and rumble removal (add a 40 Hz to 120 Hz cut). If
there is nothing plugged into the side chain jack at the back of the unit, it connects the opposite
channel's signal to the detector and uses it for control, making this channel reduce amplitude (or
duck) when a signal is present on the other channel. Adjust the compressor controls for the desired
amount of action. When the side chain is active the LED will illuminate.
(12) BYPASS: This is a hard wired bypass switch that connects the input jack directly to the output
jack (same type only). The 1/4" jacks are connected together and the XLR jacks are connected
together. Bypass will not function for 1/4" input to XLR output or XLR input to 1/4" output. When the
bypass is enabled the LED will illuminate.
(13) STEREO LINK: If the compressor is to be used with stereo signals, the link switch should
be pressed. It sums the RMS detector voltages together for an accurate representation of the two
levels, and locks the channels together to maintain the stereo image during compression. When
the link switch is pressed, all of channel A’s controls except the output level affect both channels.
The controls for channel B are disabled except its output level. As a reminder of this, the gain reduction meter for channel B is disconnected. The gain reduction meter for channel A is accurate for both
channels and should be used to monitor VCA activity. When the stereo link is enabled the LED will
illuminate
(14) POWER SWITCH: Power is applied when this switch is pressed. As with all devices, the
power to external devices should be applied first, then the mixer and finally the power amp to
minimize turn on transients.
(15) POWER LED Indicates that AC mains power is connected and power switch is in the on
position.
5
INPUT AND OUTPUT JACKS:
(16) BALANCED OUTPUT: XLR servo balanced output. The nominal level (when the output meter
is at 0 dB) is +4 dBu. (Pin 2 is positive in phase).
(17) UNBALANCED OUTPUT: 1/4" unbalanced output. If this jack is used, the input/output TRS
jack (#18) becomes an input only (tip) jack. The nominal level is 0 dBu.
(18) DETECTOR SIDE CHAIN INSERT: 1/4" stereo (TRS) jack which allows an external device
(such as a graphic EQ) to be inserted into the detector’s signal path. The tip has the send signal, the
ring is the return input. Aswitch in the jack normally connects the return (ring) to the other
channel’s send (tip) until a plug is inserted. This gives ducking capabilities without patching.
(19) INPUT/OUTPUT: Adual function 1/4" TRS jack that has both input and output signals configured so that a standard (not cross wired) stereo shielded cable can be used to plug into the TRS
insert of a mixer. (The tip is the compressor input, the ring is the output, which match the insert jack
wiring of all current Peavey mixers.) If the unbalanced output jack (#17) is used, the ring connection
(output) of this jack is disconnected, and it becomes an input only jack (tip). The nominal levels are
0 dBu.
(20) BALANCED INPUT: XLR balanced input for +4 dBu (nominal) line level inputs. Pin 2 is the
positive phase, pin 3 is the negative phase.
(21) A/C POWER INLET: This is the receptacle for an IEC line cord, which provides AC power to
the CEL
™
2. Connect the line cord to this connector to provide power to the unit. Damage to the
equipment may result if improper line voltage is used (see line voltage marking on unit).
NOTE: FOR UK ONLY
As the colors of the wires in the mains lead of this apparatus may not correspond with the col-
ored markings identifying the terminals in your plug, proceed as follows: (1) The wire which is
colored green and yellow must be connected to the terminal which is marked by the letter E or by
the earth symbol or colored green or green and yellow. (2) The wire which is colored blue must be
connected to the terminal which is marked with the letter N or the color black. (3) The wire which is
colored brown must be connected to the terminal which is marked with the letter L or color red.
6
21
16 17 18 19 20 16 17 18 19 20
REAR PANEL
7
CONTROL SETTING PROCEDURES
If you are starting from scratch, or have gotten something out of whack and do not know exactly
what to adjust, begin by setting the controls so that all functions are disabled. Here are the control
positions for this:
EX THRESH: min (off)
EX RATIO: min (1.1:1)
COMP THRESH: max (+20dB)
COMP RATIO: min (1:1)
ATTACK: center (50msec)
RELEASE: center (.5 sec)
LIMIT: max (off)
OUTPUT: center (0dB)
Naturally, the controls that need to be adjusted will depend on what you want accomplished. Here
are some suggestions to get you up and running - just follow the order listed, and leave the controls
in the above (disabled) positions if that particular function is not required.
1. Determine the maximum output level and adjust the limit threshold so that at the loudest
peaks the output level never exceeds this point. (The action of the limiter can be seen on
the GAIN REDUCTION METER. If it never activates, there will be no LED activity.) One way
to do this is to deliberately increase the input to the compressor until the desired maximum
level is exceeded, then turn the limit threshold control CCW until it limits it to the correct level.
Reset the input level until the peaks just barely light the gain reduction meter. An alternate
method is to turn down the limit threshold until gain reduction has just occurred, then adjust
the output level control to set the desired output level.
2. To set up a noise gate, first turn the EXPANDER RATIO control fully CW. During quiet
passages of the source (between songs, when the mics are not being used, etc.) adjust the
EXPANDER THRESHOLD CW until gain reduction is indicated (a reduction of -12 dB is a
good starting point). Re-adjust the EXPANDER RATIO to set the desired gating action when
the source changes from noise to signal. Asetting of 1.1:1 has little action and can tolerate
higher threshold settings without coloring the sound, 3:1 will cause an abrupt turn on and off
when the signal changes and will probably need a lower threshold setting to prevent the
signal from dropping off when you don’t want it to. You may have to go back and adjust the
threshold after the ratio has been changed, since the soft knee circuitry has more effect at
lower ratios, making the transition point less obvious.
3. For typical vocal compression, set the COMPRESSOR RATIO control to 4:1 (a range of 2:1
to 6:1 is common) and adjust the COMPRESSOR THRESHOLD until the desired amount of
gain reduction is seen on the meter. This is a personal preference, but continuous gain
reduction greater than 9 dB (especially with higher ratios) could be excessive and could
create pumping and breathing artifacts as the signal rises and falls. Lower ratios will have a
more gentle effect. Adjust the ATTACK control to low values to suppress leading edge spikes,
or to high values to let them through (often used to pass through the click of a drum hit). The
RELEASE control is adjusted to smooth the transition as it comes out of compression. Too
quick a release will cause the signal to sound artificial. Afast attack and a short release time
will cause the compressor to track the signal very closely (and keep the dynamic range very
limited), but can severely impact the sound. (A 50 millisecond attack, and .5 second release
time are good starting points.)
4. After all the settings are made, adjust the OUTPUT LEVEL control for a 0 dB average on the
output meter. This control can also be used to change levels to match various inputs (+4 dBu,
0 dBu, or -10 dBV) to maintain proper headroom levels. (0dB corresponds to 0 dBu at the
1/4" jacks and +4 dBu at the XLR jacks)
8
CONTROL ADJUSTMENT RANGE
Expander Threshold -80dBu to +10dBu
Expander Ratio 1:1.1 to 1:3 (gate)
Expander Attack .5 msec (fixed)
Expander Release 50 msec (fixed)
Compressor Threshold -40dBu to +20dBu
Compressor Ratio 1:1.1 (off) to infinite: 1 (limit)
Compressor Attack .5 msec to 3 sec
Compressor Release .05 sec to 3 sec
Limiter Threshold 0dBu to +20dBu (off)
Limiter Attack .5 msec (fixed)
Limiter Release 50 msec (fixed)
Output Level -20 dB to +20 dB
9
CEL™2 SPECIFICATIONS
INPUT IMPEDANCE CONNECTOR
XLR (balanced) 30k ohms XLR
Pin 1 = ground
Pin 2 = positive phase
Pin 3 = negative phase
1/4" Phone (unbalanced) 10k ohms 1/4" phone
In-Out tip = input
ring = output
(see control functions above)
THD: .01% 20 Hz to 20 Hz
(10 Hz to 80 kHz BW)
SIGNAL TO NOISE:
97 dB (+4 dBu reference level)
FREQUENCY RESPONSE:
20 Hz to 64 kHz +0 dB/-1 dB
OUTPUT IMPEDANCE:
100 ohms (XLR and 1/4")
METERS:
Four 12 segment LED arrays, two
peak LEDs
DIMENSIONS:
19" W x 9" D x 1.75" H
(48.26 cm x 22.9 cm x 4.44 cm)
WEIGHT:
7.3 lb
(3.31 kg)
POWER REQUIREMENTS:
DOM: 120 V AC 60 Hz 15 Watts Nominal
EXP: 230 V AC 50/60 Hz 15 Watts
Nominal
10
GAIN
CEL
™
2 COMPRESSOR BLOCK DIAGRAM
REDUCTION
TO CHAN B
LINK SW
RELEASE
GAIN
CNTRL V
OUTPUT
METER
BYPASS
EXPAND
RATIO
THRESH
VCA
ATTACK
RATIO
COMPRESS
THRESH
THRESH
LIMIT
TO CHAN B
LINK SW
RMS
RECTFIER
SC EXT
OUT
IN/OUT
IN
OUT
BYPASS
SIDE CHAIN
TO CHAN B
SIDE CHAIN
JACK
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